Huge Smoke Screen From My Boxster At a Track Day

[Racer Boy]

Today I ponied up and paid an independent Porsche repair place to replace my AOS, and since I thought that was the last thing to try and fix the smoking issue, I signed up for a track day next Wednesday back at The Ridge. Since that track has a lot of really long left-handers, it should be a good test to see if the problem was solved.

While I was waiting at home for the Indy to call me when they were done with the car, I was doing some more research into AOS problems. I stumbled onto this very informative thread - http://986forum.com/forums/general-discussions/36949-oil-cloud-when-running-hard.html, and there is a lot of discussion about the scavenging pumps in the cylinder heads. I started wondering if my passenger side pump was weak, because it makes sense that if the pump isn't functioning correctly, you'll get the smoke bombs in left-handers. Think about it - the scavenge pump is in the rear of the passenger side head, so after blasting down a straight at high revs, there is hard braking, followed by hard cornering to the left. The oil can't get sucked out of the head and returned to the sump quickly enough, and the AOS sucks the oil into the intake. On the driver side head, the pump is in the front of the head, so it can return the oil back to the sump easily.

My thought was to swap the pump side-to-side, just to see if that would make any difference. When I looked at the passenger side pump, I saw that it wasn't indexed to the head correctly! The pump has 1-3 (passenger side), and 4-6 (driver side) that is stamped on it. The bank that the pump is mounted on should have the correct stamping on the pump facing the crankshaft. As you can see by the picture below, it was mounted wrong! (The driver's side pump was mounted properly). It is quite possible that this has been my problem all along.

I took the pump out and installed it correctly. It looks like the pump was removed at some time in the past, as the mounting bolts were a lot less grimy than the rest of the engine. Since I have no idea of the car's past, it is a mystery why the pump was removed.

Once I finished with the pump, I went for a test drive. There is a very steep hill in my neighborhood, so I went down it at redline (in first gear) for about five seconds, then braked very hard, and then went right back to full-throttle. Not quite the same as being at the track, but I figured if the pump weren't installed correctly, it might have smoked under those circumstances. It didn't smoke, so at least I didn't make things worse!

The real test will happen next week at the track, but I'm excited that I found something that could be the root of the trouble! I'll check back and let everyone know if the issue has been fixed.

[Gelbster]

The Prime Suspect in identifying the cause was ..........guess whoo....yup Jake !
"The pumps are also installed incorrectly in their bores or the body is disassembled and phased incorrectly into the housing."
"Is the pic of the scavenge pump taken on bank 1 or bank 2 of the engine? Its not totally clear.
Have you taken the scavenge pump apart? It is symmetrical and the body can be assembled out of phase and still fit, but have this symptom. "
Here is a reason why the mistake may have occurred -I stumbled into it when I rebuilt my engine. I was fanatical about marking everything with a paint pen. Both scavenge pumps look identical - but they are not -quite Unless you have studied the long Post by Insight on Timing as if your life depended on it ,you could easily miss it as a noob. I did but luckily caught myself.
This is a good example of the standard of work required on these cars. If you think it is "just nuts & bolts-like any other car" ,you'll fail.
Kudos to Jake and Racer Boy for doing the research.Thanks for Posting this because we tend to fixate on the AOS and X51 baffles for symptoms like this smoking.
See pge 7 photos, Post 91 scroll down for the exact photo required here:
http://rennlist.com/forums/996-forum/672370-engine-rebuild-part-3-the-finale-7.html
See Waynes comments alongside Fig 25 here:
http://www.pelicanparts.com/techarticles/Boxster_Tech/16-ENGINE-Camshaft_Swap_and_Chain_Tensioner/16-ENGINE-Camshaft_Swap_and_Chain_Tensioner.htm
and
http://www.pelicanparts.com/techarticles/Boxster_Tech/Disc163/BoxsterTech-163.htm

[911monty]

Good find. Indexed as it was the discharge port was no longer positioned correctly. I had started thinking along this line after reading your posts. I have attached your thread to patssie's thread about AOS hope you don't mind. Today I searched scavenge pumps and apparently this is not uncommon.